Once the Automatic-Backup feature is enabled on your account's upload-settings page (which requires saving the new settings), a new link will appear near the Automatic-Backup pulldown-menu: "Perform initial backup".
Clicking this link will exhaustively backup every resource which exists on your account, that has not already been backed up.
Note that the opposite action, of clearing your backup, currently requires contacting our support team.
If you have already done some backups to Cloudinary but would like to move your backups to a bucket that you own, please contact our support team. Support will need to assist with clearing existing backups so that your entire set of assets can be backed up to your bucket.